1. Field of the Invention
This invention relates to a cassette tape magazine, and more particularly to a magnetic tape cassette having an improved structure to stably feed a magnetic recording tape.
2. Description of the Prior Art
Generally a magnetic tape cassette includes a hollow plastic casing composed of lower and upper halves coupled together to provide a space for accommodating a magnetic recording tape therein. In the space, there are provided a pair of flat base plates or friction sheets between which a pair of cores are rotatably mounted. The magnetic recording tape is wound on the cores and is fed from one core to the other. The tape is guided by a pair of fixed guide pins and a pair of rotatable guide rollers which are vertically mounted in the casing. Furthermore, the flat base plates serve to guide the lower and upper side edges of the tape. In the front face of the casing, there is provided an opening through which a recording and reproducing head of a tape recorder is inserted. On the opposite sides of the opening are provided a pair of vertical support pins which cooperate to hold the tape in contact with the magnetic head when the head is inserted through the opening. Between the pair of support pins is provided a pad which is supported on a spring plate and against which the magnetic recording tape is pressed by the head. In order to obtain good quality reproduction, the magnetic tape must run in contact with the head at a suitable pressure and at a predetermined position with respect to the head. When the tape is not in contact with the magnetic head at a sufficient pressure, or when the tape is moved out of its predetermined position with respect to the head, the frequency characteristics and other input-to-output relationships are changed.
Since said plastic casing and guiding means are assembled by means of screws or ultrasonic welding, it is very difficult to fix the flat base plates in exactly flat positions or to mount the fixed guide pins and the rotatable guide rollers in exactly vertical positions. Therefore, the tape is liable to move in the direction of its transverse axis with respect to the head while the tape runs.
In a conventional magnetic tape cassette, said guiding means such as the guide pins and the guide rollers, and the pair of support pins, have straight surfaces and therefore do not function to keep the tape running in its predetermined desirable position.
The movement or deflection of the tape in the transverse direction thereof may occur when the position of the tape cassette changes, e.g. from a vertical position to a horizontal position. Furthermore, a displacement of the tape with respect to the head also occurs when the tape cassette is turned over to change the track of the tape in recording or reproduction.
Furthermore, the thinner the tape, the more frequently the lateral movement of the tape occurs. In order to reduce the size of the magnetic tape cassette, it is desirable that the magnetic recording tape be as thin as possible.
Accordingly, there is a great demand for a magnetic tape cassette in which even an extremely thin tape such as C-120 type and C-180 type can be stably fed without any deflection of the tape.